Since time unknown, black holes had been one of the greatest enigmas of the cosmic world. Black holes are like giant cosmological baskets that accept everything that manages to fall into them and never let them escape. Decades have passed since their discovery, yet they hold a special fascination among humankind. Even world-renowned physicist Stephen Hawking couldn’t resist their mysterious charm and once lost a wager over the black hole Cygnus X-1. By the way, do you know that our very own Milky Way Galaxy has a supermassive black hole at its center?

1. Black holes do not suck in objects. They have an extremely strong gravitational force which is almost impossible to overcome by any object that comes too close to it. If our Sun was replaced with a black hole of equal mass, the planets would orbit around the black hole as they orbit the Sun today.

In popular media, black holes are depicted as space entities that act as vacuum cleaners by sucking everything near it in. But this is not true. Actually, black holes are an extremely dense point in space that leads to deep gravity sinks. The gravitational force of this region is so strong that even light cannot escape. Anything, be it a planet or star, that ventures close to it immediately falls into a gravitational tug-of-war. But the object must be fairly close to the black hole to lose this tug-of-war and fall into it.

To understand the concept better, imagine replacing our sun with a black hole. One might think that all the planets and moons would be sucked into it immediately. But if the black hole is of similar mass as our sun, then all planets would continue to orbit around it absolutely unperturbed. The only thing that will change is the temperature and brightness as the planets will be quite less warm and illuminated. (12)

2. Black holes come in all sizes ranging from stellar to supermassive. They can grow throughout their lives and can eventually evaporate over time as a result of Hawking radiation.

The starting size of black holes varies depending on their source of inception. The stellar black hole originates when a large star collapses and continue to compress. The stellar black holes are relatively smaller than others but incredibly dense. The intermediate black holes are mid-sized. They form when stars in a cluster collide in a chain reaction. Several of these can form in the same region eventually falling together in the center of a galaxy creating a supermassive black hole. Our own galaxy, the Milky Way, has its own supermassive black hole at its center. After formation, these black holes keep gathering gas and dust around them. Since these materials are available in plenty in the center of galaxies, the black holes grow to enormous sizes.

Black holes do not keep on growing forever. In 1974, Stephen Hawking theorized that black holes radiate some particles, mainly photons, through a process called “Hawking Radiation.” Due to Hawking radiation, black holes keep on losing mass and began shrinking. This is an extremely slow process. It is so slow that a black hole with the mass of our Sun would take 1067 years to evaporate completely. (123)

3. Light bends so much near black holes that if you were near one and looking away from the hole you could actually see the back of your own head!

The extreme density of black holes ensures that not even light escapes from it. Light traveling near black holes immediately gets absorbed into it. But scientists have found that there is a point close to the black hole where light would not get lost. The light traveling at this point should be just slow enough to be caught by the gravity of the black hole, but should also be just fast enough so that it doesn’t get pulled into the black hole. If light can reach this point and at the exact speed, then instead of getting lost into the black hole, it will start orbiting the black hole. This point is known as the “photon sphere.”

Theoretically, if a person is at this point and turns his head to the side so that he is no longer facing the black hole, then light bounces off the back of the person’s head, orbits the black hole, and comes all the way back allowing the person to see the back of their head.(12)

4. The process of getting torn apart by a black hole is called “Spaghettification.” The tidal forces inside a black hole are so strong that they will stretch the human body into a long thin noodle of composite atoms as the person descends into it.

Have you ever thought what would happen if a person ever descended into a black hole? According to astrophysicists, the person will become an actual human spaghetti. Black holes possess extreme tidal forces. When a person enters a black hole’s event horizon, the first thing he will feel is the sensation of being pulled apart. This occurs due to the strong gravity and low gradient of gravity inside the black hole. These factors will start stretching the person in an unpleasant manner.

If the person falls feet first into the black hole, then the gravity at their feet would be stronger than at their head. So, the person would be stretched vertically. Also, the right side of the body will be pulled to the left and vice-versa, compressing the person horizontally. The vertical pull and horizontal compression will turn the person into a human spaghetti. That’s why this process is called spaghettification or “the noodle effect.” (12)

5. Black holes can sometimes eject stardust falling into it in long and bright radiation-laden burps.

In 2011, astronomers observed a burst of high-energy gamma rays. It was ejected from the center of a dwarf galaxy situated 3.8 billion light-years away. In visible light and infrared wavelengths, it was as bright as a hundred billion Suns. According to astronomers, the gamma rays radiated were the result of a star being shredded by a black hole. The star got too close to the black hole and was unable to escape its gravitational pull. The supermassive black hole that was shredding the star was ten million times the mass of the Sun.

As the star fell into the black hole and neared its maw, it heated up along the way producing a burst of energy. This energy emerged as huge amounts of bright radiation. Supermassive black holes are present at the center of most large galaxies, but events such as a “stars getting eaten” in a galaxy rarely happens, only maybe once every hundred million years. (source)

6. If you watch an object or a person slip into a black hole, no matter how long you watched, you would never actually see the object enter it due to time dilation.

The outermost boundary of the black hole is known as the “event horizon.” When seen from outside, nothing can be seen of the black hole beyond the event horizon. This horizon is a point of no return as beyond it, the gravitational pull is so intense that nothing can escape. When a person or an object approaches the black hole, for an outside observer, it appears to slow down as it approaches the event horizon. The object also appears to stretch and contort as if it is being viewed under a giant magnifying glass.

As the object reaches the event horizon, the observer would see it freeze as if someone had hit the pause button. The object would seem to remain motionless and plastered across the surface of the event horizon. The observer would realize that the object doesn’t quite pass through the horizon. As time goes by, the object would appear more and more red-shifted, and it would appear that the object would be reduced to ash before reaching the darkness of a black hole. (12)

7. About 12 billion light-years away there exists a black hole that holds at least 140 trillion times the water in all of Earth’s oceans combined making it the largest known reservoir of water.

In 2011, two teams of astronomers discovered a black hole located more than 12 billion light-years away holding the largest reservoir of water. This black hole is a feeding black hole located in a quasar called “APM 08279+5255.” It is 20 billion times more massive than our Sun. It powers the quasar by consuming the surrounding disk of dust and gas. Occasionally, it belches out energy equivalent to a thousand-trillion Suns. This black hole is surrounded by water equivalent to 140 trillion times all the water in the world’s ocean. The water is present in a vaporized state spanning hundreds of light years.

The amount of water vapor and other gas such as carbon monoxide present in this quasar is enough to feed the black hole until it grows to about six times its current size. But this might not happen if some of the gas ends up condensing into stars or getting ejected by a quasar. (source)

8. A black hole produces extremely powerful space winds blowing at 125 million kph restricting the formation of stars in the galaxy.

In 2016, astrophysicists at York University detected ultrafast, quasar winds swirling around a supermassive black hole, PDS 456. The winds were blowing at more than 200 million kilometers an hour, roughly, a quarter the speed of light. The speed of the wind is equivalent to a category 77 hurricane. It is occurring as spiraling matter, and the heat and light from the quasar blow it away from the black hole.

These space winds play an important part in galaxy formation. During the formation of galaxies, these winds push material such as dust and gas outwards deterring the creation of stars. In absence of these winds, there would be far more stars in big galaxies than they actually are. Also, these powerful winds regulate the growth of the black hole itself. (12)

9. There exists a black hole in the Perseus Cluster that “sings.” It produces the lowest note in the universe to the tune of a B-flat that’s 57 octaves below middle C.

In the Perseus cluster of galaxies located 250 million light years away, there exists a supermassive black hole producing the lowest note ever recorded. The note was first recorded in 2002 using NASA’s Chandra X-ray Observatory. Among the observations, astronomers saw the presence of ripples in the gas filling the cluster. These ripples were the sound waves that traveled away from the cluster’s central black hole.

The pitch of the sound generated by this supermassive black hole is in the note of B-flat. But the note is 57 octaves lower than middle-C making it impossible for the human ear to hear it. Nonetheless, it is the lowest note ever detected from an object in the Universe. (source)

10. On April 2019, scientists successfully captured the first image of a black hole located in the Messier 87 galaxy 55 million light years from Earth. Its event horizon is 3 million times the size of our planet which is larger than our entire solar system.

Since light cannot escape from black holes, it is almost impossible to photograph them. They are surrounded by glowing accretion disks of in-falling material due to which one can understand that the black part in the center of the disk is the black hole. Recently, scientists have achieved the impossible by actually photographing a black hole. The first picture of the black hole is the outcome of a series of processes. In April 2017, data was collected by the Event Horizon Telescope, a network of eight, radio telescopes. These telescopes were located from Antarctica to Spain and Chile. They picked up radiation from particles that swirl around the black hole at close to the speed of light.

Creating the black hole image was the tricky part. It involved the combined effort of more than 200 scientists. The result was released for public viewing in April 2019. The image shows a fuzzy, doughnut-shaped ring of gas and dust. This is the black hole’s accretion disc that feeds the black hole within. The crescent-like halo in the image is due to the particles in the side of the disc rotating towards Earth. It looks brighter as its particles are flung towards us faster. The dark shadow within is the edge of the event horizon. Beyond it, no light or matter can travel fast enough to escape the gravitational pull of the black hole.

The photographed black hole is located at the heart of the Messier 87 Galaxy located 55 million light-years from Earth. Scientists are trying to produce an image of the black hole in our Milky Way. (12)

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